1. Field of the Invention
The present invention relates to an article for oil sorption, and more particularly, to an article having a plurality of interstitial spaces formed from a plurality of adhered cross-linked polymer particles and to a method for making the same.
2. Description of the Prior Art
Contaminated surfaces resulting from spilled oil pose a severe threat to the environment. Such oil spills are found both on land and water. Oil pools collect around above ground storage tanks and in the ground around under ground storage tanks and oil transportation pipes. Oil spills also occur from tanker and underwater oil drilling accidents as well as smaller spills in harbors, rivers, waterways and other navigation channels resulting from the daily loading, unloading and storage of oil throughout the world.
Oil spills on water bodies are particularly serious. Besides contaminating the surface of the water body and posing a significant risk to waterfowl, surface oil invariably reaches and contaminates the adjoining land. Even if the adjoining land is not contaminated, with time, the oil will settle as conglomerates at the bottom of the water body, thus destroying plants and other forms of aquatic life.
Various methods have been proposed and used for removing spilled oil from both land and water. These methods include mechanical skimmers, microorganisms that consume the spilled oil, and detergents. Skimmers require complex machinery; microorganisms can only be used within narrow environmental constraints, and detergents pose other environmental hazards. In view of these drawbacks, sorbent articles are increasingly becoming the preferred method of recovering spilled oil. Such sorbent articles and materials presently used include straw and ground corn cobs, some mineral adsorbents like perlite, and clays, as well as oil absorbing polymers.
It has been known for sometime that vulcanized rubber and other types of cross-linked polymers will absorb oil and organic vapors to a varying degree. Examples of such use are disclosed in U.S. Pat. No. 4,728,343 issued to Syder, U.S. Pat. No. 3,567,660 issued to Winkler, U.S. Pat. No. 4,039,489 issued to Fletcher et al. and U.S. Pat. No. 4,182,677 issued to Bocard et al.
U.S. Pat. No. 4,728,343 discloses a method of absorbing organic vapors in a storage container by suspending ground rubber particles in a mesh net. The rubber particles absorb the vapors so that the vapor concentration does not approach an explosive level.
U.S. Pat. No. 3,567,660 discloses a method for absorbing oil spills with shredded or ground rubber from automobile tires. The tires are ground to a particle size between 1 and 10 mesh. The Winkler patent teaches that rubber particles larger than 1 mesh have a tendency to sink in water, while particles smaller than 10 mesh dissolve quickly in oil. When the shredded rubber particles are applied to spilled oil on a contaminated water surface, the particles swell from the imbibed oil and coagulate to form conglomerates. In the preferred embodiment, the shredded rubber tires are combined with powdery polystyrene. The Winkler patent teaches that this addition speeds absorption of the spilled oil.
U.S. Pat. No. 4,039,489 discloses a method for absorbing oils with polymer particles having a minimal amount of cross-linking. In the preferred embodiment, the mean chain length of the polymer between cross-linking sites is recommended, at a minimum, to be at least 4,000 chain atoms long. Although the Fletcher et al. patent teaches that minimal cross-linked polymers absorb oil readily, the resulting absorbent is physically weak when swollen with oil. When used to absorb an oil spill on water, the polymer tends to break apart. To overcome this problem, the Fletcher et al. patent teaches coating a fiber or fabric substrate with the minimal cross-linked polymer. The fiber substrate provides a support structure.
Another method for producing oil absorbing polymers is disclosed in U.S. Pat. No. 4,182,677. This patent teaches that rubber particles of the size 0.1 to millimeters can readily absorb hydrocarbons or organic liquids if the particles are first subjected to organic or inorganic acid solvents. The patent teaches that rubber particles are created by using crushers or by grinding the rubber waste after cooling it to a very low temperature, for example, in liquid air. To enhance the absorption of oil, the rubber particles are treated with a mineral or organic acid. The rubber particles are stored in suspension in a pure acid or diluted acid solution. After filtration, the rubber particles are washed with water in order to remove the acid. In U.S. Pat. No. 4,182,677, the treated rubber particles are stirred in suspension with a mechanical stirrer or through convenient shaping of the container apparatus. The patent teaches that it is advantageous to use rubber waste of a density lower than 1.5 so that, after the hydrocarbons have been absorbed, the rubber particles rise to the surface.